Means for measuring the energy of alternating-current circuits.



, N0.'180,545. PATENTED JAN. 24, 1905. l

M. WALKER. MEANS EUR MEASURING TEE ENERGY 0E ALTERNATING CURRENTCIRCUITS;l

APPLICATION FILED FEB. 28. 1903.

Y z1 v .Y A WTIESSES: l [NYE/(TOR nro/mer.

UNITED STATES Patented January 24, 1905.

PATENT OFFICE.

MILES WALKER, OF VVILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC t MANUFACTURING COMPANY, A COR- 4PORATION OF PENNSYLVANIA.

MEANS FOR MEASURING THE ENERGY OF ALTERNATIN-CURRENT CIRCUITS.

SPECIFICATION forming part of Letters Patent No. |780,545, dated January24, 1905.

Application filed February 28, 1903. Serial No. 145,618.

T0 all' 'Lv/tom t may concern:

Be it known that LMILEs WALKER, asubject of the King of Crreat Britain,residing at Wilkinsburg, in the countyof Allegheny and State ofPennsylvania, have invented a new and useful Improvement inV Means forMeasuring the Energy of Alternating- Current Circuits, of which thefollowingis a specilication.

My invention relates to the measurement of the energy ofalternating-current circuits; and it has for its object to provide acomparatively simple and inexpensive means which may be readily adaptedto a wide range of voltages in such manner as to secure accurate resultswithout the waste of any considerable amount of energy in the apparatus.

The wattmeter which I propose to use is of the electrostatic type,sometimes designated as a quadrant electrometer, the essentialcharacteristics of which are set forth in the published transactions ofthe Royal Society of the year 1891, Vol. 182, page 519. Instruments ofthis character have not been heretofore generally used, because theforces'which act upon the needle or movable member of the A instrumentwhen the instrument is connected up in accordance with the ordinarymethod are so small as to necessitate the employment of an instrumentwhich is extremely delicate and sensitive. Underl the ordinary practicethe voltage which is applied to the quadrants of the instrument issecured by passing'the main current through a non-inductive resistance,and this necessitates the utilization of a low voltage in the instrumentin order to avoid a largeloss of poweriin the non-inductiveresistancewhich would otherwise result. Furthermore, with the usual arrangement anerror is introduced into the reading of the instrument which isproportional to the square of the voltage. The connections employed byme insure a voltage between the quadrants that is larger than thevoltage hitherto employed, so that comparatively large forces may beutilized in the instrument and the 1 objections to the use of largevoltages which In the accompanying drawings, which illustrate myinvention, Figures l, 2, and 3 are diagrams illustrating threearrangements of apparatus in accordance with my invention. Fig. 4 is asimilar diagram, but embodies in addition a compensating transformer.Figs.

5 and 6 are views, respectively, in side elevation and in section, ofthe compensating transformer illustrated diagrammatically in Fig 4.

In Fig. 1 I have shown an alternating-current generator 1 as supplyingenergy to one or more translating devices 2 through conductors 3 and 4,land in order to measure the energy of the circuit 3 4 I employ anelectrostatic wattmeter 5. the needle or movable member 6 of which isconnected directly to the side 4 of the circuit and the quadrants orstationary members 7 and 8 of which are connected to the respectiveterminals of a noninductive resistance 12. The non-inductive upon thenature of the circuit, as does also the number of ohms represented bythe noninductive resistance 12, the latter being also dependent upon theconstant of the instrument. The main object to keep in view in fixingthe particular values of resistance and transformation ratio is toobtain sufficient voltage at the terminals of the resistance and yet toavoid any considerableloss. rIhe greater the ratio of transformation theless will be the loss; but the ratio of transformation should be keptwithin reasonable limits or the magnetizing-current in the transformerwill form too large a fraction of the whole current.

In Fig. 2 the several parts of the apparatus and their circuitconnections are the same as I have shown in Fig. 1, except that I haveshown the non -inductive resistance 12 as having its middle pointconnected to the conductor 3.

I have also shown in this figure a condenser i 14 interposed between theneedle or movable member 6 of the wattmeter and the conductor 4, thisdevice being provided in order to adapt the apparatus to exceptionallyhigh vp1- tages, and if the condenser is so made that its capacity maybe changed the constant of the instrument may be thereby adjusted.

In Fig. 8 I have shown an autotransformer 15 in lieu of the two-coiltransformer, (shown in Figs. 1 and 2,) the primary portion 15L of whichis substantially one-half of its length, and a non-inductive resistance16 is connected in shunt to this primary portion of the transformer. Theentire length of the transformerwinding, which constitutes thesecondary, is connected to the stationary members or quadrants 7 and 8of the wattmeter 5 in the same manner as is indicated in the precedingiigures. This form of my invention while differing somewhat in itsstructural features is substantially the same as regards ratio ofcircuits and operation as those shown in the other figures.

Referring now to Figs. 4, 5, and 6, the several parts shown in Figs. 1and 2 are reproduced in Fig. 4, except that the middle points of thetransformersecondary 9 and of the non-inductive resistance 12 areconnected together and to the conductor 3. In addition to these featuresI here employ a compensating transformer 17, the primary winding 18 ofwhich is in series with the primary winding 11 of the transformer lO andthe secondary winding 19 of which is connected in series between thesecondary 9 and the quadrant S of the wattmeter 5.

Since the middle point of the secondary 9 and that of the resistance 12are of the same potential, either or both of these points may beconnected to the conductor 3 in each of the modifications shown in Figs.1, 2, and 4.

While I have shown the middle point of the transformer-secondary 9 andthe middle point of the non-inductive resistance 12, or one of them, asconnected to the conductor 3 and the needle or movable member 6 of thewattmeter as connected to the conductor 4 in each of Figs. 1, 2, 8, and4, it will be understood that a reversal of these connections is equallyoperative and within the scope of my invention.

In Figs. 5 and 6 I have shown in detail the structural features of thecompensating transformer 17, it being composed of a laminated core 20and the primary and secondary windings 18 and 19, already referred to.The sccondary winding 19 of the compensating transformer consists of afew turns of line wire and occupies a small amount of space. The primarywinding 18 consists of a few turns of wire or strap-copper sufiicientlylarge to carry the main current. The object of the transformer 17 is togenerate in the secondary winding a small electromotive force whichshall be proportional to and in phase with the magnetizing-currentflowing in the primary windin l l of the transformer 10 at all ranges ofload from a small fraction of full load to full load on the transformer10. In older to make the matter clear, we will assume that thetransformation ratio of transformer 10 is the ratio one to one. As iswell known, in the operation of a series transformer (designed to take asmall magnetizing current) the secondary of which is closed on anon-inductive resistance a current iiows through the non-inductiveresistance, which is almost in phase with the current in the primary.There is, however, a difference of phase between the primar Y andsecondary currents, owing to the fact that the primary current besideshaving a component equal to the secondary current must also have acomponent at right angles in phase to the secondary current, thatcomponent being` required to magnetize the core of the transformer` Thiscomponentof the primary current, which is at right angles to thesecondanv current, is here called the magnetizingcurrent" of transformer10. For the purpose of zuljusting the compensating transformer 17 itisdesirable to measure the magnetiZing-current of transformer 10 under alloperating conditions of load. This current may then be plotted in acurve, taking the main curve through the winding 11 as abscissaa. Forexample, let the magnetiZing-current of transformer 1d be c amperes of acertain frequency when the load of transformer 10 is C am peres. Let thevoltage across the resistance 12 be represented by V when the maincurrent C passes through the winding 11. ln the natural operation of thetransformer the magnetizingcurrent c is subtracted from the current (iso far as effect on the secondary line o1 the transformer is concerned,so that the voltage V, which is in phase with the secondary cnrrent, isnot strictly in phase with the current C. All that is necessary tocorrect this is to provide a small electromotive force in the winding19, so that it adds the small voltage e to the larger voltage V, thusmaking Y-l-p very nearly in phase with the current (si, That is requiredof the compensating transformer is to generate in the seeomlary 1.) a

small voltage e, such that 1' *fwn The (j V -l- 'e current c should beas nearly as possible in phase with the voltage w. In order to insurethe performance of the desired function by the compensating transformer,it ina.\Y be provided with an air-gap 21, so that a consider ableinagnetizing-cnrrentin translbrmer 17 is required. The main current (iis the niagnetiZing-current in the compensating transformer 17, becausethere is no load on the secondary. The nnignctizing-current n ol thetransformer 10 is nearly ninety degrees be- IOO llO

hind the current C, and the voltage e is also nearly ninety degreesbehind the voltage V, so that the current c and the voltage o are verynearly in phase. The quantity of iron and copper and the number of turnsfor the transformer 17 are so chosen as to provide the desired voltage uin accordance with methods well known in the art. If the current c isproportional to the current C. an ordinary air-gap is all that isrequired. In general the current c will not be exactly proportional tothe current C. In such case it is desirable to 'partially short-circuitthe air-gap 21 with a few laminae of iron, as indicated at 22 inFig. 6,the result being that when the current C is small and the iron notsaturated the voltage o may be larger in proportion. It is thuscomparatively easy by experiment to adjust the amount of iron whichshort-circuits the air-gap so that the voltage v follows a law veryclosely resembling the law of the current c.

In each of the forms of circuit connections shown the one side of thedistributing-circuit or one terminal of the translating device receivingenergy lfrom the source, as will be seen,l is connected to a point ineither the main transformer-secondary or the non-inductive resistance inshunt thereto which is midway in potential between the quadrants of thewattmeter, and consequently the error ordinarily produced by a highvoltage between the quadrants is eliminated.

I claim as my inventionl. rI he combination with a source of alternatingcurrents and a translating device supplied thereby, of atransformer-having its primary winding in series between the source ofcurrent and the translating device, a static wattmeter having itsquadrants connected to the terminals of the transformer-secondary,

a non-inductive resistance having its terminals connected to theterminals of the transformer-secondary and circuit connections betweenthe respective terminals of the translating device and the needle of thewattmeter and a point having the same potential as the non-inductiveresistance.

2. Means for measuring the energy of alternating-current circuits,comprising an electrostatic wattmeter having its movable memberconnected to one side of the circuit, a series transformer in the otherside of the circuit having its secondary terminals connected to thequadrants of the wattmeter and a non-inductive resistance having itsterminals connected to those of the transformersecondary and having itsmiddle point connected to they main circuit between the transformerandthe translating device.

l3. In an alternating-current circuit, the combination with a yseriestransformer and a non-inductive resistance, of an electrostaticwattmeter having its stationary members connected to the terminals ofthe non-inductive resistancev and the transformer-secondary and havingits movable member connected to the opposite side of the main circuitand a connection between the transformer side of the main circuit andone or more points in the apparatus which have the same potential as themiddle point of the non-inductive resistance.

4. In an alternating-current circuit, an electrostatic wattmeterconnected in circuit through a series transformer and a non-inductiveresistance.

5. In an alternating-current circuit, an electrostatic wattmeter havingits movable member connected to one side of the circuit and atransformer and non-inductive resistance interposed between thestationary members of the wattmeter and the other side of the circuit.

6. The combination with an alternating-current circuit, of anelectrostatic wattmeter having its needle or movable member connected toone side of said circuit, a transformer having a winding connected byits middle point to the other side of said circuit and by its ends tothe quadrants or stationary members of the wattmeter and a non-inductiveresistance connected in shunt to said transformer-winding.

7. The combination with an alternating-current circuit and anelectrostatic wattmeter for measuring its energy, of a transformer andnon-inductive resistance interposed between the wattmeter and one sideof said circuit and a condenser between the same and the other side ofthe circuit. l

8. The combination with an alternating-current circuit and anelectrostatic wattmeter for measuring its energy having its movablemember connected to one side of the circuit, of` a transformer and anon-inductive resistance having end connections to the quadrants of thewattmeter and a connection between the transformer side of the maincircuit and one or more points in the apparatus having the samepotential as the middle point of the noninductive resistance.

9. The combination with an alternating-current circuit and anelectrostatic wattmeter having its movable member connected to saidcircuit, of a transformer having its primary winding in the otherside ofsaid circuit and the terminals of its secondary windingconnected to thestationary members of the Wattmeter and a non-inductive resistance inshunt relation to said secondary winding, and a connection between themain circuit vand one or more points in the apparatus having the samepotential as the middle point of the non-inductive resistance.

10. The combination with an alternatingcurrent circuit and anelectrostatic wattmeter for measuring its energy, of a seriestransformer having its primary in said circuit, a non-inductiveresistance in shunt to the transformer-secondary and a compensatingtrans- IOO IIO

former having its primary also in said circuit and having its secondaryconnected in series between the first transformer-secondary and astationary member of the wattmeter, the nonindnctive resistance and theiirst transformer-secondary being connected to another stationary memberof the wattmeter and a connection between the main circuit and one ormore points having' the same potential as the middle point of thenon-inductive resistance.

l1. A compensating transformer having a Core provided with a partiallyshort-circnited but permanent air-gap. A

12. A compensating transformer having a core provided with an air-gapand with nonadjustable means for partially and permanentlyshort-circuiting said gap.

MILES WAL RER.

NTitiiesses:

JAMns B. YOUNG, .BIRNEY HiNEs.

